Piston



Jan. 21; 1930. F. M. MOORE PISTON Filed Feb. 12, 1929 INVENTbR 1 MM!) are BY Q m I ATTORNEY Patented Jan. 21, 1930 UNITED STATES PATENT OFFICE FRED M. MOORE, F OAKLAND, CALIFORNIA, ASSIGNOR. TO ECONOMY OIL SLOT PISTON COMPANY, OF RENO,

NEVADA, A CORPORATION OF NEVADA PISTON Application filed February 12, 1929. Serial No. 339,471.

This invention relates to gas engine pistons and particularly represents modifications over the structure shown in my copending application for patent, Serial No. 389,472, filed Feb. 12, 1929, the purpose of the present invention being the same as that in said other invention, namely to eliminate oil pumping.

A further object of the invention is to produce a simple and inexpensive device and yet one which will be exceedingly elfective for the purpose for which it is designed.

These objects I accomplish by means of such structure and relative arrangement of parts as will fully appear by a perusal of the following specification and claims.

In the drawing similar characters of reference indicate corresponding parts in the sev eral views:

Fig. 1 is a fragmentary sectional elevation of a gas engine piston associated with its necessary rings, showing the piston on its down or suction stroke.

Fig. 2 is a similar view showing the on an upward stroke.

Fig. 3 is a fragmentary sectional plan on the line 33 of Fig. 1.

Referring now more particularly to the characters of reference on the drawings, the numeral 1 denotes the upper body portion of the piston in which the usual annular ring grooves 2 are cut. The usual skirt 3 is provided below said upper portion, in which the wrist pin bearings 4 are mounted, and being somewhat separated from the upper portion by air slots 5 or similar passages cut through just below the lower ring grooves, and which prevent the formation of a vacuum seal be tween the bottom of the skirt and said groove.

Cut in the lower surface of the ring groove above the lowest one, or in the upper face of the land between the two lowermost grooves is a continuous groove 6, slots 7 bepiston I 5 ing cut from the interior of the piston at intervals to communicate with the bottom of said groove. A bypass passage 8 is drilled from each slot intermediate its ends to the top surface of the lowest ring groove adjacent the back, while openings 9 are drilled at intervals from the back of such groove at the bottom to the interior of the piston.

On the downward movement of the piston during the suction stroke the pressure in the cylinder above the piston is considerably less than that in the interior of the piston, as will be evident; the latter pressure being substantially atmospheric.

The compression rings 10 which frictionally engage the cylinder walls are relatively retarded in their downward movement and their upper faces are consequently tightly engaged with the upper faces of the grooves, leaving clearance between their lower faces and the bottom of the grooves, as shown in Fig. l.

The tendency for the greater pressure below to force oil up into the cylinder past the upper rings is therefore broken at the groove 6 by reason of the slots 7, while leaving the oil about the lowest ring undisturbed, so that such oil forms the necessary pressure-tight seal around the piston at that point. The above conditions obtain as long as the slots 7 remain open and if they could be depended onto thus remain open the bypasses 8 would be unnecessary.

I have found from experience however that such slots do not remain open but quickly fill with oil, draining into the same from the groove 6. This oil will not then drain back into the piston onaccount ofthe relatively high pressure in the same against which the oil must flow. There is therefore a tendency for such oil to be forced upwardly into the groove 6 and then upwardly into the cylinder, defeating the end which it is desired to attain.

The bypass or relief passage 8 is therefore provided, which functions during the upstroke of the piston to keep the slots 7 clear of the oil and prevent the same from filling up, so that on the alternating downward strokes of the piston the undesired oil pumping action is eliminated.

On the up-stroke of the piston the previous conditions are reversed and the rings are now clear of the tops of their grooves and are tightly sealed against the bottom of the same, so that the second ring 10 seals the top of the groove 6.

It is impossible therefore for the oil from the groove 6 and slots 7 to drain back into the cylinder if .it were not for the bypasses 8, since the pressure in the piston presses against the oil outlets at the inner ends of the slots 7. By reason of each bypass however an open oil passage is formed from the groove 6 to the passage 9 and the interior of the piston; said passage comprising the slot 7, the bypass 8, the space between the lower ring and its groove both at top and back, and said passage 9. The pressure in the piston is of course exerted evenly against the inner ends of the openings 9 and the inner ends of the slots 7, so that the pressure at the openings 9 tending to force oil upwardly is neutralized by the pressure at the slots tending to force the oil down. Gravity therefore aided by the upward momentum of the piston in the opposite direction allows the oil to flow down from the slots 7 to the interior of the piston through the lower openings 9, thus eflectually preventing the slots 7 remaining full of oil.

On the downward stroke of the piston when the conditions are again reversed the slots 7 are therefore clear of oil so as to provide the necessary vacuum break, the small amount of oil still remaining in the groove 6 being only sufiicient for the necessary ring and cylinder wall lubrication.

From the foregoing description it will be readily seen that I have produced such a device as substantially fulfills the objects of the invention as set forth herein.

YVhile this specification sets forth in detail the present and preferred construction of the device, still in practice such deviations from such detail may be resorted to as do not form a departure from the spirit of the invention, as defined by the appended claims.

Having thus described my invention what I claim as new and useful and desire to secure by Letters Patent is:

1. A piston comprising a hollow body having spaced annular ring grooves, a continuous groove cut in the bottom of a ring groove other than the lowermost one, passages from said continuous groove to the interior of the piston, and a bypass from each such passage to the top of the ring groove directly below the one having such continuous groove; there being openings from the back of said last named ring groove to the interior of the piston.

2. A piston comprising a hollow body having spaced annular ring grooves, a continuous groove out in the bottom of a ring groove, passages from said continuous groove to the interior of the piston, and passage means from said passages to the interior of the piston arranged to allow of a flow of oil from said passages to the interior of the piston when said continuous groove is sealed by the ring in the corresponding ring groove.

In testimony whereof I affix my signature.

, FRED M. MOORE. 

